Excellent remark ( as nearly always from you ) . sometimes the obvious can be front of our eyes but we keep on looking for the improbable difficult possibilities
The reason why this CB tripped is not relevant. The worrying thing is that no one noticed the CB was tripped during the event prior to the landing. The crew were apparently in contact with engineers on the ground, it is surprising that no one had a look at the wiring diagram and noticed the altn gear ext circuit is protected by two fuses.